Gasoline compositions



nited States Patent GASOLINE COMPOSITIONS Byron M. Vanderbilt,Westfield, John P. Thorn, Union, and George E. Serniuk, Roselle, N. J.,assignors to Essa Research and Engineering (Zompany, a corporation orDelaware No Drawing. Application April 27, 1955 Serial No. 504,343

Claims. (Cl. 4456) This invention relates to an improved gasolinecomposition and more particularly to a gasoline containing substantialamounts of butanes and butenes and a mixture of isopropyl and secondarybutyl alcohols.

it has been known in the past to include minor proportions such as aboutl2.5% of isopropyl alcohol in gasoline forthe purpose of impartinganti-stalling properties by the prevention of carburetor ice formation.This property is particularly valuable for fuels used in operatinginternal combustion engines during cold, humid weather.

One disadvantage of employing small proportions of isopropyl alcohol hasbeen its tendency to increase the vapor pressure of the gasolinecomposition in which it is included. Consequently, in order to produce agasoline containing isopropyl alcohol which would be of sufliciently lowvapor pressure as not to have an undesirable vapor-lock tendency, ithas, been found necessary to decrease the concentration of volatilehydrocarbons such as butanes and butenes. Such a decrease or backing-outof butanes is highly undesirable from an economic standpoint, sincethese highly volatile fractions are relatively plentiful in modernrefinery operations and possess high octane characteristics.

The effect of small quantities of isopropyl alcohol on the vaporpressure of gasoline is somewhat unexpected. Isopropyl alcohol has aReid vapor pressure of 1.9 p. s. i. and is miscible with gasoline in allproportions. Gasoline normally has a Reid vapor pressure of 7.15 p. s.i. so that the addition of a soluble component of lower vapor pressurewould be expected to effect a net vapor pressure decrease. Actually, anabrupt vapor pressure increase occurs upon the addition of l4% by volumeof isopropyl alcohol. One possible explanation of this anomaly is thatthe isopropyl alcohol molecules, which are known to exist as dimers orhigher polymers because of co-ordinated valences, are broken down intoindividual molecules on being highly diluted by a nonpolar medium suchas gasoline. The individual alcohol molecules would be expected to exerta much higher vapor pressure than the polymer existing when the alcoholis in pure or highly concentrated form.

The content of butanes in gasoline generally varies between about 4% toabout 20% by volume, depending on the season during which the gasolineis to be used. Summer grade gasoline intended for use and storage-duringwarm weather should be of the lowest volatility, having a Reid vaporpressure of about 7 to 10 p. s. i. and a C content of 48%. Spring gradefuels are more volatile, having a Reid vapor pressure of 11 to 12 p. s.i.

and containing about 9-12% C hydrocarbons, while winter gasolines, whichare the most volatile, have a Reid vapor pressure of 13 to 15 p. s. i.and a C; content of l318%. Since the present invention makes it possibleto retain substantial amounts of butanes in the gasoline while adding aneffective amount of isopropyl alcohol, and, in some cases, to actuallyincrease the butane ice content without raising volatility, the greatestadvantages are to be gained in its application to the volatile wintergrade gasoline. However, the present invention may also be used inpreparing less volatile spring and summer grade fuels.

It has now been found that by the inclusion of small percentages ofsecondary butyl alcohol into gasoline fuels containing isopropylalcohol, the undesirable vapor pressure rise usually associated with thepresence of isopropyl alcohol can to a large extent be alleviated and insome cases a gasoline of overall reduced volatility produced, so thatadditional butanes may be included without adversely affecting thevapor-lock characteristics of the fuel. It may be that this unexpectedefiect is the result of re-association of the isopropyl alcoholmolecules in the gasoline blend due to the addition of butyl alcohol.This explanation is presented as a hypothesis only.

It is an object of the present invention, therefore, to provide agasoline fuel composition containing substantial amounts of butanes andat the same time possessing desirable anti-stalling characteristics andhaving sulficiently low vapor pressure as not to cause undesirable vaporlock when used in internal combustion engines.

It is a further object of this invention to provide a gasolinecomposition containing isopropyl and secondary butyl alcohols in whichthe fuel has improved octane rating characteristics.

A still further object of this invention is to provide a stable motorfuel containing isopropyl and secondary butyl alcohols havingsatisfactory power output characteristics when used in internalcombustion engines.

These objects, as well as others which will be in part pointed outspecifically and in part apparent from the subsequent description, areattained by providing a gasoline composition containing mixtures of fromabout 2 to 12% by volume of a blend of isopropyl and secondary butylalcohols in which the ratio of isopropyl alcohol to secondary butylalcohol is preferably from about 1:1 to about 1:3.

In the past, it has been customary to evaluate the volatility ofhydrocarbon mixtures such as gasoline in terms of so-called Reid vaporpressure. In measuring the vapor pressure of gasoline blends containingisopropyl alcohol, the introduction of either water or water saturatedair into the system may seriously affect the total vapor pressure. Inthe regular Reid vapor pressure method for an all-hydrocarbon gasolinein which a water phase is present, the two immiscible liquids exertadditive vapor pressures. However, when a water-soluble material such asisopropyl alcohol or secondary butyl alcohol is present, thedistribution of such a component between the water and gasoline phasesmay have a pronounced effect on the total vapor pressure. Furthermore,in making up blends of gasoline with such compounds as alcohols, themechanical loss of some of the butanes prescut is difiicult to avoid,thus seriously afiecting the vapor pressure of the final compositions.In view of this, a more exact method of measuring vapor pressure hasbeen developed, and since the results of a number of tests utilizing thevapor pressures thus obtained are set forth in the ensuing description,the special apparatus and method of operation used will be describedsomewhat in detail. All of the vapor pressure data presented in theensuing description for gasoline-alcohol blends are based upon thisrefined method as described below. When Reid vapor pressures areemployed, they will be specified as such. It has been found that theReid vapor pressures are generally proportional to those vapor pressuresdetermined by the method to be described, so that an increase in vaporpressure produced by a particular combination of alcohols in a gasolinewould also reflect an ahydrocarbon in,;the, PICSEIICQOf water.;components-are mutually insoluble, they. exist as, separate --;phases'and, consequently, the vapor pressures of the two components areadditive. the-hydrocarbon can be obtained by applying the appro-"ass-ease The.,apparatus.employed,for the-.vaponpressure det rminations.comprisedz'a metal jacketed Seltzer. ,b'Qttle .o .abopt.1 3 O ml.capacity fitted with ajspecial adapter carrying, a gauge. reading from0. to 15 p. s. i. pressure and a self-sealing rubber diaphragm assembly'through =which.successive samples couldbe withdrawn from, or ,aldtledvto, a-single charge .of gasoline by; means of a hypodermicneedle. .A:calibrated blow-case was used to introducethe original sample into thebottle (or the bomb, as it may.be.called)-against a dry nitrogenatmosphere.

- :A constant temperature: water; bath fitted with -an, elec-Jtronically controlled immersion heater and an air-driven stirrer-wasused to maintain the temperature in the bomb constant at IOOLF.

qlBeforeeach determination, a record was made of the y rqom-temperature, barometer reading and. initial temperature of the bomb;The bomb was sealed at a pressure of one atmosphere after beingthoroughly flushed ,withdrygnitrogena It wasthen heated at 100 F. to,equilibrium. pressure with respect to the room and the pressure wasrecorded in p. s. i. g. If the observed pres- :sure corresponded to thepressure calculated due to temperature differential, the bomb wasconsidered in. suitablec ondition for use; It was then cooled in icewater and-a 265 mlrsample was-introduced intothe bomb from v thecalibrated blow case. The sample was charged against .the nitrogenatmosphere in the bomb. The bomb was then placed in the 100 F. bath andreadings were taken 7111, accordance with the procedure well known inthe Reidmethod. V g I 7 -Equilibrium pressure was assumed when threesuccessive five-minute periods gave the same reading. Blends of thegasoline were then made in the bomb by .introducing'a-calculated amountof alcohol through the v.rubber diaphragm bygmeans of a hypodermicneedle.

- Before each addition, an equivalent volume of gasoline ,91 blend wasfirst removed from the charge in order ,to

=-maintain; a constant volume in .the bomb. The, direct reading in p.s.,-i. g. was observed on thegauge and observed values were correctedfor-initial temperature -difierent-ial and compressibility of thenitrogen: These :values, as stated before, are close to the true vaporpressures-of the gasolines'and generally comparable to Reid1vaporpressure-readings, although they are believed to be considerablymore accurate.

The conventional Reid method for determining vapor .-,pr ess u res-.;of:petroleum, products, ASTM jdesignation .13 323, Federal specification1(\ '/'.Li-79l) method: 1201, =is&;based on-the measurementof the..Vapor pressure of Thus the vapor pressure of priatecorrection for thevapor pressureof water; However, ifthis method and procedure, are.applied to a sys- -tem comprising a hydrocarbon, water, and, a third,

mutually soluble component such as a lower. aliphatic alcohol, the vaporpressure will be in'error, since the -vaporpressures will no longer beadditive. The water ,present will be: distributed between a'phasecontaining the majorportion of the water, the mutually solublecomponent, and some hydrocarbon, and a phase containing ..the-.majorpart of the hydrocarbon, mutually soluble com- .ponent, and water. Or,if there is a suflicieut propor- -tion of the mutually soluble alcoholadded, it will 'solubilize the water and hydrocarbons tovgive onephase.

" The existence of such phases is dependent uponthe water content, whichin the Reid method is indeterminant.

Thus the true vapor pressure of a hydrocarbon blended with awater-soluble component cannot be measured accurately by the Reidmethod.

Since thejtwo 1 8:%;., .-F 136 3% -F 139 .10% 11- 143 148% 9F 23g 42% rF 240' F 242 38%,.-. ".F 351 2% ,-F -,356 297%" ;F 361. Percent recoveryi 97.0 :Percent resid 1 0 Pereentloss 2 G a y AlI. V, 58.9 Reid vaporpressure .'.L 9.7

v the tollowing percentages of theiindicated additive were The presentmethod described measures the vapor pressure of the strictly drycomponents in a dry, inert atmosphere. This method also provides for theintroduction to, or removal of samples from, a single charge ofgasoline, a feature which minimizes sample errors due to opening of thebomb whencharging due to loss of low boiling hydrocarbons during thisprocess.

-,In,preparing-,gasoline nigrtures in accordance with the even m ler.afi ut t less a l t f rolumeiimy be employed by gl e usion ,of a smallquantity'of secondary. butyl alcohol n the fuel. This will beillustrated in a b equen examp has been found ,that, the effect, ofsecondary butyl alcohol in lowering the vapor pressure of agasoline-isopropyl alcohol blend to which it is added is not merely oneof counteracting the correpen n i QI VQPQE-P QSP ffe t o op opy o Datain the subse'quent exampleswill illustrate that, a marked synergisticflifict takes place, resulting in much s in r ase: inh he v por pressureof a I gasoline, than isopropyl alcohol but containing some secondary,butyl alcohol are employed, L

EXAMPLE I in f h sbza ii ff lii c ba Si having The lowing inspectionswas mixed with various percentages of 99% i wmnrlalwhql swa -5 1W S nd bt alcohol respectively, but not mixtures of the two.

.Ellfl" eit qt qit'peic' t distilld j. .Various of alcohols were addedto the base stock and thefiaptarprssure measured in p. s. iflg. Thevalues. given..as AP ..represent the change in vapor employed.

.'1AB LE.I...1. APatyolume'percentageadditive 1 ...indicated(p..s.,i.g.) Composition 7 he .f s.

'oa'sounewmrbprd ilaiiofioijln 0175 piss lolsi 1'0. Gasoline-[secondarybutyl alcohol 0.06 '0.12 0.25 O.31

. the above itmight beexpe ctednthat the addition to a base gasoline;stgckcf 8% totaLalcohol comprising a mixture of 6% isopropyl alcohol and2% secondary Thus, the amount of isopropyl alco here'the addi n of onlya small amount butyl alcohol based on the gasoline would result in a netvapor pressure increase of 0.75 p. s. i. (the sum of a +0.81 p. s. i.due to the isopropyl alcohol and 0.06 p. s. i. due to the secondarybutyl alcohol). This is not the case, however, as is illustrated byTable II below. In obtaining the data for this latter table the samegasoline base stock Was mixed with blends of isopropyl and secondarybutyl alcohols in various volume percentages and using various ratios ofisopropyl alcohol to'secondary butyl alcohol. These results, in terms ofchanges in vapor pressure (AP), are given below.

TABLE II Volume Change in Ratio of isopropyl alcohol to secondary butylpercent of vapor alcohol additive pressure used (AP) in p. s. i.

1/l0 ll 0. 50 1/5" 12 -0.44 l/4 5 0. 12 1/4 l0 0. 19 1/3 4 0. 18 1/3 8O. 12 1/2 3 0. 25 1/2 6 0. 13 1 2 0. 32 1.. 4 0.38 1 6 0.25 1 8 0. 19 22 0. 50 2 4 0. 50 2 6 0. 44 2 8 0. 37 3 2 0. 50 3 4 0. 50 3. 6 0.50 3.-.8 0.19

Thus, instead of an overall vapor pressure increase of 0.75 p. s. i., aswould have been expected to have resulted from the addition of 8% of a3:1 mixture of isopropyl and secondary butyl alcohols in the absence ofa synergistic effect, a vapor pressure increase of only 0.19 p. s. i.resulted. It will be noted by making other comparisons that in all casesthe increase in vapor pressure obtained by using the mixture ofisopropyl and secondary butyl alcohols was less than would be expectedon the basis of the individual alcohols themselves. This difierential of0.56 p. s. i. is equivalent to 1.1 volume percent of butanes. Therefore,instead of backing out 1.43% butanes, which would be necessary tomaintain vapor pressure of the original base gasoline on the basis ofthe expected 0.75 p. s. i. increase due to the additive mixture, it isnecessary to back out only 0.33 volume percent butanes to cancel the0.19 p. s. i. actual increase. Thus, the advantages of the additives areobtained without the sacrifice of the expected amount of butanes.

1n the most preferred embodiments of the invention, the alcohols areadded in such quantities as to produce an actual overall decrease in thevapor pressure. This means that additional butanes can be added to thegasoline and the desired volatility still maintained. To obtain thisresult the mixture of alcohols added must contain more secondary butylalcohol than isopropyl alcohol and a substantial amount of the mixturemust be employed. This does not adversely affect the fuel value of thegasoline, since as much as about 12% by volume of the alcohol mixturemay be employed without appreciably lowering the calorific content ofthe resulting blend. Secondary butyl alcohol also contributes to theelimination of carburetor icing, especially when used in conjunctionwith isopropyl alcohol. Mixtures of equal volumes of isopropyl andsecondary butyl alcohols are as effective in preventing carburetor icingas is isopropyl alcohol alone. For this reason, it is not alwaysnecessary to include as much as l2.5% of isopropyl alcohol in thegasoline to prevent carburetor icing. It may also be desirable in somecases to employ blends containing less secondary butyl alcohol thanisopropyl alcohol, even though a net vapor pressure increase results,since this increase is less than the predictable value. In mostinstances 28% by volume of a blend of the alcohols will be incorporatedinto the gasoline. However, to obtain a vapor pressure decrease the useof blends containing at least about three times as much secondary butylas isopropyl alcohol by volume'is preferred.

EXAMPLE II Although secondary butyl alcohol is the preferred additivefor gasoline-isopropyl alcohol blends, it has also been found thatmixtures of secondary and tertiary butyl alcohols also may be employedadvantageously in some cases. The useof such mixtures is of greateconomic advantage, since in commercial operations mixtures of thesecondary and tertiary butyl alcohols are commonly produced as such. Thefact that mixtures of secondary and tertiary butyl alcohols may producea net lowering of vapor pressure is an especially unexpected result,since the tertiary alcohol alone has a pronounced tendency to increasethe vapor pressure of a gasoline to which it is added. In Table IIIbelow, a gasoline base stock was mixed with various percentages ofisopropyl alcohol and various percentages of mixtures of isopropylalcohol with mixed tertiary and secondary butyl alcohols. The Reid vaporpressures of these mixtures were determined and it was found that blendsof isopropyl alcohol with the mixture of tertiary and secondary butylalcohols often resulted in a net vapor pressure decrease.

TABLE III Modified 1 Composition Reid vapor pressure in p. s. i. g.

Base stock 14. 2 Base stock plus 2% isopropyl alcohol. 14. 6 Base stockplus 4% isopropyl alcohol. 14, 3 Base stock plus 8% isopropyl alcohol14. 2 Base stock plus 4% of a 50/50 mixture of tertiary and secondarybutyl alcohols... 13. 6 Base stock plus 2%iso1 hol and 2% of a 50/50mix- 40 ture of tertiary and secondary butyl alcohols. 13.7

Base stock plus 4% isopropyl alcohol and 4% of a ture of tertiary andsecondary butyl alcohols 13, 2

1 No Water present.

The addition of the mixed butyl alcohols effects a not decrease in vaporpressure of 0.5 p. s. i. in one case and 1.0 p. s. i. in the other.Thus, 0.95% by volume and 1.90% by volume respectively of butane couldbe added to these blends While maintaining the volatility of the fuel ata constant value.

EXAMPLE ill In addition to providing a beneficial effect in regard tovapor pressure or volatility characteristics of gasoline, secondarybutyl or tertiary butyl alcohols provide an improvement in performancecharacteristics, especially with respect to octane number. In Table IVgiven below, a base gasoline stock containing 2.2 cc. per gallon oftetra ethyl lead was mixed with various percentages of secondary butylalcohol and tertiary butyl alcohol, giving The research blending octanenumber is defined as the research octane number of the blend minus thevalue obtained when the research octane number of the base stock ismultiplied by t1 1e fraction of base stock in the blend and Elieblliiggrence divided by the fraction of blending agent in It will be undrstood, lot c ur tha :th s con a y butyl akoholmaybesrippliejd eitherpure or'in ad with" other butyhalcohols suchias is'obutyl or butylalcohols, as ,well as =With+tertiarybutyl alcohol. Thebasic-gasolinestockrnay also contain inaddi tion :to certain conventional materialssuch as t etraethyl;-lead or other alkyl lead anti-knock gents andconventional scavenging agents of the type conventionally employedWhenftetraethyl lead is used, such other additives as solvent oils, guminhibitors; oxidationfinhibitor s, and thelike. l: v v i i' N While theinvention has been described with respect to 'variou s specific'compositions, it will be, of course, understood thatit' is not to be solirnited'but isto include such reasonable equivalents as may be includedwithin the scope of the appended claims.

Whatis clair'ned'i's: i

l. A gasoline'con position consisting essentially of a hydrocarbon basestock boiling in thegasoline range,

hydrocarbons, about 1% to about 3%by volume of isopropyl alcohol andabout 1% to about 9% by volume of'secondary'butyl alcohol.

'2. gasoline composition consisting essentially of hydrocarbons boilingin the gasoline range,'about 4% to about 20% by volume of C aliphatichydrocarbons, and about 1% to 12% by volume ofisopropyl' alcohol andsecondary butyl alcohol in th'e ratio of about lzl to 1:3.

about' -4% to about 20% "by volurne of C aliphatic 3. A ga o ine isqfi.ascllg ae iaz 2 ii; is

. about 1:3. U a I 5- A asol n hav n R vis van r ressu e mo e fl a bou 5Pmmds Pe s uar n l 9 28 essenti ly f; a hyd o ar w as tq kwa gasoline range, --abqut 4% to. 20% by volume I ,s. 29 aliphatic y bons. nd ab u 1%t .2 y 3 0 of a mixture of isopropyl alcohol and secondary butyl h l, sam xture i n f h ee imes a mu s t ondary butyl alcohol as isopropylalcohol.

References Cited in the file of this'patent V UNITED STATES PATENTSAlcohol, A Fuel-for Internal GOmbuStiQn Engines,

by s. 1; W. Pleeth, Chapman .and HallL td, 1949; page 83.

o P19131 11; iQahiPhltb. rt s 1 f s nm y a q l 9. se a ar h t l 7 9 45

1. A GASOLINE COMPOSITION CONSISTING ESSENTIALLY OF A HYDROCARBON BASESTOCK BOILING IN THE GASOLINE RANGE, ABOUT 4% TO ABOUT 20% BY VOLUME OFC4 ALIPHATIC HYDROCARBONS, ABOUT 1% TO ABOUT 3% BY VOLUME OF ISOPROPYLALCOHOL AND ABOUT 1% TO ABOUT 9% BY VOLUME OF SECONDARY BUTYL ALCOHOL.